Intracavity Sum-frequency Generation Research Articles

Highly efficient continuous-wave solid-state Raman crystal lasers at 555 and 559 nm

High-power efficient continuous-wave Nd:YVO4/KGW Raman lasers at 555 and 559 nm are achieved by using a double-sided dichroic coating output coupler to improve the resonance quality factor. The Np-cut potassium gadolinium tungstate (KGW) is used to generate the Stokes waves at 1159 and 1177 nm by placing the polarization of the1064 nm fundamental wave parallel to the Ng and Nm axes, respectively. The lithium triborate (LBO) crystal with the cut angle in the XY plane for the type-I phase matching is used to perform the intracavity sum frequency generation for yielding the green light at 555 nm and the lime light at 559 nm at the optimal phase matching temperature. Experimental results were systematically accomplished to comprehend the optimal cavity length for the conversion efficiency. Under the optimal cavity length, the output powers can reach 6.6 and 6.3 W at a pump power of 22 W for the wavelengths of 555 and 559 nm, respectively. The conversion efficiencies can be up to 30% and 28.6% for 555 and 559 nm, respectively.

Compact efficient high-power continuous-wave Nd:YVO4/KGW/LBO Raman lasers for selectable wavelengths within 559-603 nm

Compact efficient high-power continuous-wave Nd:YVO4 Raman lasers for selectable wavelengths within 559-603 nm are achieved by using KGW crystal for intracavity stimulated Raman scattering (SRS) and lithium triborate (LBO) crystal for intracavity sum frequency generation (SFG) and second harmonic generation (SHG). The LBO crystal with the cut angle in the XY plane for the type-I phase matching is used to perform intracavity SHG or SFG. Experimental results reveal that the participated Stokes lines include the internal vibration mode at 901 cm-1, the external vibrational mode at 209 cm-1, and the combination mode of the 901 cm-1 and 209 cm-1 Raman shifts. By tuning LBO temperature for attaining the maximum output power, the output spectrum reveals the triple peaks of 588.7, 595.7, and 603.1 nm with the intensity ratio of 10:4:1. Under this circumstance, the output power can reach the highest value of 10.8 W at a pump power of 40 W. Furthermore, the output spectrum can be simply concentrated on the single peaks among 588.7 (orange), 565.7 (yellow), and 559.1 nm (lime) by tuning LBO temperature to fulfill the selection of the critical phase matching. The output powers at a pump power of 40 W can be up to 8.0, 6.1, and 9.8 W for the single-peak emission at 588.7, 565.7, and 559.1 nm, respectively. Finally, a dual-peak emission of 565.7 and 572.3 nm with total output power of 5.2 W can be generated by tuning LBO temperature to match the SFG for 572.3 nm.

Compact continuous-wave solid-state Raman lasers at 707 and 714 nm for laser trapping and cooling of atomic strontium and radium.

Two compact laser sources at 707 and 714 nm are realized efficiently by using a diode-pumped a-cut Nd:YVO4 laser with intracavity stimulated Raman scattering and sum-frequency generation (SFG). The fundamental wave at 1342 nm is generated by the 4F3/2 → 4I13/2 transition in Nd:YVO4 crystal. The Raman Stokes waves at 1496 and 1526 nm were obtained by placing the c-axis of the Nd:YVO4 crystal along the Ng and Nm axes of an Np-cut KGW crystal, respectively. LBO crystals with critical phase matching are used to perform the intracavity SFG of fundamental and Stokes waves. At a pump power of 36 W, the maximum output powers at 707 and 714 nm can reach 2.72 and 3.14 W, corresponding to light-to-light conversion efficiencies of 7.5% and 8.7%, respectively. The developed 707 and 714 nm laser sources are practically useful in laser trapping and cooling related to atomic strontium and radium.

Efficient Continuous-Wave Eye-Safe Nd:GdVO4/KGW Raman Laser and Sum Frequency Generation for Deep-Red Emission

A concise, efficient continuous-wave eye-safe Nd:GdVO4/KGW Raman laser at 1525 nm is here demonstrated. A Nd:GdVO4 crystal was used to produce the fundamental field at 1341 nm and a KGW crystal generated the intracavity Stokes field at 1525 nm via wavelength conversion of stimulated Raman scattering. The output power of the Stokes field at 1525 nm could achieve 2.1 W under the pump power of 30 W. Furthermore, two different lithium triborate (LBO) crystals with critical phase matching were exploited to obtain deep-red emission at 714 nm via the intracavity sum frequency generation of 1341 and 1525 nm waves. One cutting angle was in the XY plane and the other was in the XZ plane. The empirical thermo-optical coefficients for the LBO crystal were exploited to systematically analyze the critical phase matching conditions. Numerical results revealed that the type-I phase matching angle in the XY plane was near θ = 90° and ϕ = 3.3° at room temperature, whereas the type-I phase matching angle in the XZ plane was near θ = 86.3° and ϕ = 0° at a temperature around 47 °C. The numerical values for the optimal temperatures for the two different cutting angles were found to be in good agreement with experimental results. At the pump power of 30 W, the output power at 714 nm was approximately 2.9 W by using the LBO crystal with the cutting angle in the XY plane. On the other hand, the maximum output power at 714 nm could be up to 3.2 W under the pump power of 30 W by using the cutting angle in the XZ plane. Furthermore, the linewidth of the SFG emission was confirmed to be nearly the same for the two different cutting angles. The overall linewidth could be narrower than 0.2 nm. The developed laser at 714 nm can be useful in the exploration of ionic and atomic radium isotopes with laser spectroscopy.

Wavelength-versatile deep-red laser source by intracavity frequency converted Raman laser.

We demonstrate an efficient wavelength-selectable output in the attractive deep-red spectral region from an intracavity frequency converted Nd:YLF/KGW Raman laser. Driven by an acousto-optic Q-switched 1314 nm Nd:YLF laser, two first-Stokes waves at 1461 and 1490 nm were generated owing to the bi-axial properties of KGW crystal. By incorporating intracavity sum-frequency generation and second-harmonic generation with an angle-tuned bismuth borate (BIBO) crystal, four discrete deep-red laser emission lines were yielded at the wavelengths of 692, 698, 731, and 745 nm. Under the incident pump power of 50 W and the repetition rate of 4 kHz, the maximum average output powers of 2.4, 2.7, 3.3, and 3.6 W were attained with the pulse durations of 3.4, 3.2, 4.3, and 3.7 ns, respectively, corresponding to the peak powers up to 177, 209, 190, and 245 kW. The results indicate that the Nd:YLF/KGW Raman laser combined with an angle-adjusted BIBO crystal provides a reliable and convenient approach to achieve the selectable multi-wavelength deep-red laser with short pulse duration and high peak power.

Self-mode-locking through intra-cavity sum-frequency generation.

A new technique for mode-locking is demonstrated based on two lasers sharing one leg for sum-frequency generation. When the two lasers had equal round trip time one will produce bright pulses and the other dark pulses. Both lasers used Nd:YVO4 as the gain material, but operated at different wavelengths, namely 1064 nm and 1342 nm. In the present configuration, sub-250 ps pulses were generated at a repetition rate of 276 MHz with an output power of 70 mW. With appropriate choice of round trip loss at the two wavelengths it was possible to choose which laser was generating the bright pulses.

Fast-tunable femtosecond visible radiation via sum-frequency generation from a high power NIR NOPO.

We report on a high power ultra-broadband, quickly tunable non-collinear parametric oscillator with highly efficient intra-cavity sum-frequency generation. It simultaneously delivers femtosecond pulses in two synchronized output beams: up to 4.9 W tunable from 650 to 1050 nm in the near infrared and up to 1.9 W from 380 to 500 nm in the visible spectral range. The (to our knowledge) novel source is ideally suited for spectroscopy or multi-color imaging. First results of two-color functional microscopy are presented.

A Wavelength Tunable CW Orange-red Laser Source Based on Magnesium Oxide-doped Periodically-poled LiNbO3 in an Intracavity Sum-frequency Generation

A watt-level continuous wave (CW) orange-red laser with wavelength tunable properties is experimentally implemented based on sum-frequency generation (SFG) in a composite cavity. The cavity is composed of an 880 nm laser diode (LD) side-pumped Nd: GdVO4 p-polarized 1062.9 nm cavity and a single-resonant optical parametric oscillator (SRO) of signal light using a magnesium oxide-doped periodically-poled LiNbO3 (MgO: PPLN) crystal with a poling period of 29.1 μm. In the overlap region of the two cavities, orange-red laser is generated by using a type-II critical phase-matched potassium titanyl phosphate crystal (KTP) crystal. In the temperature tuning range of the MgO: PPLN crystal (from 30 °C to 200 °C), the CW orange-red laser beams are generated in a tunable waveband from 612.24 nm to 620.72 nm (Δλ = 8.48 nm), corresponding to the mid-infrared idler light is also obtained with tunable wavelength from 4027.5 nm to 3708.2 nm (Δλ = 319.3 nm). At the lowest tuning temperature of 30 °C, the maximum CW output power of the orange-red laser at 612.24 nm and the idler light at 4027.5 nm are obtained, which are 1.145 W and 2.83 W, respectively.

All-Solid-State Q-Switched Laser Operating at 294.6 nm

We report a stable high-power all-solid-state Q-switched laser operating at 294.6 nm with a pulse width of 24 ns and a repetition rate of 20 kHz produced by intracavity sum-frequency generation and external frequency doubling in LiB3O5 and β-BaB2O4 crystals, respectively. Upon synchronizing the fundamental lasers, the maximum output power at 589 nm is 1.2 W, which is frequency doubled to produce up to 167.8 mW at 294.6 nm, thereby providing a conversion efficiency of 13.98%.

Optimization of sum frequency output from intra-cavity sum frequency generation in singly resonant optical parametric oscillator

Theoretical investigation and optimization of output characteristics of intra-cavity sum frequency generation between pump and the signal waves in singly resonant optical parametric oscillators (IC-SFG-SROs) are presented. Under the collimated Gaussian beam approximation, simple models considering different spatial orderings of SRO and SFG processes of IC-SFG-SROs are set up. The calculations based on experimental parameters are in good agreement with experimental results. Output characteristics of IC-SFG-SROs operated at other wavelengths are optimized and predicted. For given experimental conditions (pump wavelength, pump power and SRO crystal length), the optimum length of SFG crystal and SF power are calculated, respectively. Furthermore, when a periodically poled crystal with a cascaded pattern is used as the SRO crystal and SFG crystal, the optimum SFG crystal length and the SF power are also calculated. These calculations and models provide guidelines for designing and optimizing continuous-wave tunable IC-SFG-SROs.

Tunable ultraviolet vortex source based on a continuous-wave optical parametric oscillator

We report a continuous-wave (cw) optical parametric oscillator (OPO) generating optical vortices tunable in the ultraviolet (UV). Based on MgO:sPPLT as the nonlinear crystal, the singly resonant OPO is pumped by a cw vortex beam in the green, and deploying intracavity sum-frequency generation (SFG) between the undepleted pump and the Gaussian resonant signal in the crystal of BiB3O6, it can generate optical vortices of order, luv=1 and 2, tunable across 332-344nm in the UV with a maximum power of 12mW. Due to conservation of orbital angular momentum in the parametric process, the OPO also produces a non-resonant idler output beam in a vortex spatial profile of order li=1 and 2, identical to the pump vortex, with the signal beam in Gaussian distribution. The idler vortex is tunable across 1172-1338nm with maximum output power of 1.3W.

Intracavity sum-frequency generation of a 795 nm pulsed laser with a short pulse width based on two MgO : PPLN crystals

We report a 795 nm tunable pulsed laser with intracavity sum-frequency generation (SFG) based on an optical parametric oscillator (OPO) pumped by a 1064 nm laser. The cavity consists of two periodically poled MgO : PPLN crystals, the periods of which are 22.0 and 31.0 μm. The crystal with the period of 31.0 μm is used to generate a mid-IR beam, while the other crystal is used for SFG of the pump beam and the mid-IR beam. The pulsed width of the 795 nm laser is 3.6 ns, and the repetition rate of the laser is 35.3 kHz. The peak power of the laser is 2.8 kW with a linewidth of 0.35 nm. The 795 nm laser threshold pump power is 1.4 W and the optical-to-optical efficiency of 1064 nm to 795 nm is 5.7% at a maximum output power. The laser is supposed to be a kind of a competitive near-IR laser source for studying a diode-pumped rubidium laser.

Theoretical analysis of a continuous-wave 323 nm laser generated by a singly resonant optical parametric oscillator with intracavity sum-frequency generation

Theoretical calculations of a singly resonant optical parametric oscillator (SRO) with intracavity sum-frequency generation (SFG) (IC-SFG-SRO) are presented to obtain tunable ultraviolet laser radiation at 323 nm. Under the plane-wave approximation, simple models considering different spatial orderings of SRO and SFG processes are set up. The calculations are in good agreement with the experimental results, and some important simulation parameters are also obtained. According to these parameters, the output characteristics of the 532 nm green laser pumped SRO with an intracavity SFG between the pump and the resonant signal near 822 nm and the 1064 nm infrared laser pumped SRO with an intracavity SFG between the pump and the resonant signal near 1644 nm are predicted and optimized. The models and simulation parameters provide guidelines for optimizing the continuous-wave IC-SFG-SRO.

Implementation of bright six-partite entanglement by coupled intracavity sum frequency generation

Bright six-partite continuous-variable (CV) entanglement generated by the coupled intracavity sum frequency generation is investigated. The entanglement characteristics of reflected pump fields and the output sum frequency fields are discussed theoretically in symmetric and asymmetric cases by applying van Loock and Furusawa criteria for multipartite CV entanglement. Such compact tunable multipartite CV entanglement, generated from an experimentally feasible coupled system, could be used in integrated quantum communication and networks.

Coherent detection of THz laser signals in optical fiber systems

Terahertz (THz) coherent detectors are crucial for the stabilization and measurement of the properties of quantum cascade lasers (QCLs). This paper describes the exploitation of intra-cavity sum frequency generation to up-convert the emission of a THz QCL to the near infrared for detection with fiber optic coupled components alone. Specifically, a low cost infrared photodiode is used to detect a radio frequency (RF) signal with a signal-to-noise ratio of approximately 20dB, generated by beating the up-converted THz wave and a near infrared local oscillator. This RF beat note allows direct analysis of the THz QCL emission in time and frequency domains. The application of this technique for QCL characterization is demonstrated by analyzing the continuous tuning of the RF signal over 2 GHz, which arises from mode tuning across the QCL's operational current range.

Wavelength tunable CW red laser generated based on an intracavity-SFG composite cavity

We report a wavelength-tunable watt-level continuous wave (CW) red laser that uses a composite cavity based on an intracavity sum-frequency generation (SFG). The composite cavity is composed of a LD side-pumped Nd: GdVO4 p-polarized 1062.9 nm resonant cavity and a resonant optical parametric oscillator (SRO) of s-polarized signal light using a periodically poled crystal MgO: PPLN. Based on the temperature tuning from 30 °C to 200 °C, the CW red laser beams are obtained in a tunable waveband from 634.4 nm to 649.1 nm, corresponding to a tunable output waveband from 3278.0 nm to 2940.2 nm of the mid-infrared idler lights. The maximum CW output power of the red laser at 634.4 nm and the idler light at 3278.0 nm reach 3.03 W and 4.13 W under 30 °C, respectively.

Fiber-laser-based, high-repetition-rate, picosecond ultraviolet source tunable across 329-348 nm.

We report a compact, fiber-laser-based, high-repetition-rate picosecond source for the ultraviolet (UV), providing multi-tens of milliwatt of average power across 329-348 nm. The source is based on internal sum-frequency-generation (SFG) in a singly resonant optical parametric oscillator (OPO), synchronously pumped at 532 nm by the second harmonic of a picosecond Yb-fiber laser at 80 MHz repetition rate. Using a 30-mm-long single-grating MgO:sPPLT crystal for the OPO and a 5-mm-long BiB3O6 crystal for intracavity SFG, we generate up to 115 mW of average UV power at 339.9 nm, with >50 mW over 73% of the tuning range, for 1.6 W of input pump power. The UV output exhibits a passive rms power stability of ∼2.9% rms over 1 min and 6.5% rms over 2 h in high beam quality. Angular acceptance bandwidth and cavity detuning effects have also been studied.

Effects of resonator design on the efficiency of singly-resonant optical parametric oscillator with intracavity sum-frequency generation

We present a theoretical model to investigate the performance of an intracavity sum-frequency generation (SFG) inside the ring resonator of a singly-resonant optical parametric oscillator (SR-OPO) scheme. The effect of the resonator specifications on the efficiency of such SFG–OPO configuration is modeled and simulated by solving the coupled equations in a normalized from which describe simultaneous SFG and OPO interactions inside two individual phase-matched nonlinear crystals. Numerical simulation is carried out using real practical values associated with experimental results that are recently reported by Devi et al. (Opt Express 21:24829–24836, 2013). We found very good agreement and consistent with the used experimental data, indicating the validity of our simulation. The influence of the beam waist of interacting beams on the conversion efficiency of resultant SFG–OPO radiation is investigated through introducing a magnifying factor that relates optical and physical characteristics of the designed SFG–OPO configuration. It is found that when this factor is taken equal to 3, the maximum of normalized SFG power reaches to ~0.0034 for an OPO loss of ~10 %. This is very consistent with the measured value of ~0.0030, confirming that our represented model is valid. The SFG–OPO arrangement is then optimized by extracting a mathematical formula that relates the optimum magnifying factor to the gain parameters of OPO and SFG interactions.

LDA抽运腔内LBO和频激光器噪声特性分析

LDA抽运腔内LBO和频激光器噪声特性分析

494.5 nm generation by sum-frequency mixing of diode pumped neodymium lasers

We report a coherent radiation at 494.5nm by intra-cavity sum-frequency generation of 912nm Nd:GdVO4 laser and 1080nm Nd:CaYAlO4 laser. Blue laser is obtained by using a doubly folded cavity, type-II critical phase matching KTP (KTiOPO4) crystal sum-frequency mixing. With total pump power of 33W (13.8W pump power for 1080nm Nd:CaYAlO4 laser and 19.2W pump power for 912nm Nd:GdVO4 laser), TEM00 mode blue laser at 494.5nm of 1.6W is obtained. The power stability in 30min is better than 3.5%.